Unfortunately one any one map I can only put water alpha layer for one of them...Acid got it. So Lava and Poison have the Acid overlay (if you want, just copy the Traces in the entities/lava and entities/poison over the one in the entities/acid to try the other water overlays).

Acid, Lava, and Poison all do the same damage to a tank. Acid is the Purple/Yellow one. Poison in the Green. Lava is red.

Unfortunately the very edge of the Poison pit has a bit of the Acid texture on it. Also unfortunately since all 3 pits had to be a slightly different depth to allow the textures to be different, Lava isn't underwater and Acid is barely under water.

Last, Lava sometimes doesn't notice you are on its texture (could be due to my having 6 textures in use! Most maps use 4).

Again, this is NOT for more then ONE tank! This is just a test.

Right now I've been thinking is a great thing to use to surround team bases - injure anyone trying to leave by the non-standard route. A small river width zone will kill 30-50% of your health (from full). The pits in the above map kill 100% by the time you cross it (oh well...it was a test of the graphics and working not of anything else).